Industry has recognized an important need for implementing product tracking systems which perform essentially from the commencement of manufacture to the point of shipment of completed goods. For such tracking, an effective code and code reader system is required having a very high population capacity, as well as a capability for being read by reading devices. For example, a tire manufacturing facility may produce 40,000 tires per day with a need for separate codes on each tire item.
Bar codes have been widely employed in industry for the purpose of tracking. Generally, the codes are comprised of sequences of lines or bars located over or against a white or highly contrasting background. The bars are of selectively varying thicknesses and spacing so as to be machine readable. These codes require a relatively large number of bar components, typically 20 to 22 bars being employed. However, even with such detailed bar codes, a relatively limited number of code combinations become available, for example, in the range of about 65,000. This limitation fails to supply the needs of modern industry.
Industry further is looking to codes which are generated in a dot matrix form by ink jet devices which conventionally spray a sequence of spaced dots. In many industries, ink jet marking systems are not suitable for product tracking. For example, for many the delicate equipment for spraying inks will not withstand the environment and the inks themselves will not be capable of marking many products. A dot matrix form of marking device wherein the dots are formed by indentations in the material itself has been marketed by the Assignee hereof under the trade designation "Pinstamp". These devices are described in U.S. Pat. No. 4,506,999 entitled "Program Controlled Pin Matrix Embossing Apparatus" by Robertson. Ink jet printers initially were developed for man-readable alphanumeric codes wherein the discrete dots of a matrix symbol are somewhat broadly spaced. To generate bar codes with these existing dot matrix devices requires that the printers be modified such that the dots are created in mutual tangency to form a solid bar or, alternatively, that some form of reading be developed which is capable of tracking through a singular horizontal line of code spaced dots. If the latter can be accomplished, then the dot spacing configuration of the jet printing devices can be retained for both man readable codes, as well as bar codes and the number of codes which can be developed for a given region of product carrying the code will be greatly enhanced. Further, the code population can be expanded to significant numbers in the three hundred million range. However, even the slightest inclination or tilting of the product carrying the code during a reading procedure will cause typical readers to miss the requisite horizontal line of dots.
The reading of bar codes generally involves the optical scanning of a sequence of transitions exhibited by each code. For example, in the retail trade, as items carrying the bar coded labels are presented to the clerk or checker, they are passed over an optical scanner which employs laser optics for "reading" the code and transmitting the thus-read information to a computer. For effective and reliable operation, the goods carrying the coded labels are manipulated by the checker within the defined optical scanning region until a valid "read" is achieved. Generally, a short audible pulse indicates the reception of a valid read and the rate thus required for this reading procedure is of a slow enough level to permit a real time computer analysis of the code as it is being scrutinized bar by bar. However, where code readers are employed in general industry, several difficulties are posed, inasmuch as their relative positioning or placement on the subject being tracked necessarily varies from piece to piece. Thus, the reader device is called upon to locate the code and then read it without manipulation of the piece carrying the code. Further, this reading must take place at a very rapid rate so as not to disturb the speed of the production process involved. Recently, a code reader has been introduced to the marketplace which has the unique capability of successfully reading bar codes within rigorous industrial environments. The reader, marketed under the trade designation "Numbra" by the Assignee hereof, employs a video camera and carries out code scanning utilizing the horizontal scan lines of the video derived image. Through this technique, codes which vary considerably in their placement are readily read in very rapid fashion. A need now exists to adapt this code reading system to achieve a capability for reading bar codes formed by marking systems such a ink jet printers and indentation systems otherwise employed for forming dot matrix alpha-numeric characters. It is desirable that such adaptation also be employed to achieve a capability for reading conventionally formed bar codes which have been deformed or marred in the process of production.